Conveyors may be used in systems configured to stack material or receive material from some type of excavator or feeder. Typically, systems designed for stacking material utilize a number of conveyors. One set of conveyors is typically used to convey material to a stacker for stacking in a particular area. Another set of conveyors is used to receive material from an excavator or feeder that is reclaiming the material stacked in that area or providing material extracted from a mine. Examples of systems used to stack material or reclaim material are disclosed in U.S. Pat. Nos. 7,191,888, 6,782,993, 6,155,400, 6,085,890, 5,609,397, 5,562,194, 5,090,549, 4,139,087, 3,604,757, 2,851,150 and 1,996,488, and U.S. Patent Application Publication No. 2007/0102263.
Conveyor systems used to stack material often include a system of conveying devices. For example, overland conveyors are often used to transport material over relatively long distances to different locations. An overland conveyor may be configured to move material from a material receiving location to a material discharge location.
Typically, a multi-section mobile bridge conveyor or other conveyor is positioned adjacent to an overland conveyor. An overland tripper or other device may be configured to feed material from an overland conveyor to the mobile bridge conveyor. The mobile bridge conveyor may stack the material or may move the material to a cross conveyor attached to the mobile bridge conveyor, which may stack material or transfer the material to another conveyor or a stacker for stacking the material.
Often, a mobile bridge conveyor includes and supports a tripper that is interconnected with a cross conveyor. The tripper may lift and discharge material from the mobile bridge conveyor to the cross conveyor. The tripper typically shares a conveyor belt with the mobile bridge conveyor. The tripper usually will not include a belt, but will raise the belt of the bridge conveyor to a point above and adjacent to the cross conveyor for discharging material to the cross conveyor. Typically, the tripper is moveably supported on the mobile bridge conveyor to ensure alignment and proper transport of material to the cross conveyor for stacking the material.
The cross conveyor is typically affixed to the tripper to receive material from the tripper and stack that material adjacent to the mobile bridge conveyor or transfer the material to another conveyor. The mobile bridge conveyor may be used to stack material via the cross conveyor.
A mobile bridge conveyor may also include and support a tripper that does not have a cross conveyor, but is interconnected with another piece of mobile equipment. The tripper may then discharge material directly to that other piece of mobile equipment in the same way that it may discharge material to a cross conveyor.
To stack material in irregular shaped permanent or temporary storage areas or irregular shaped valleys within a storage area, a mobile bridge conveyor may need to be moved multiple times, which can cause significant operation costs to be incurred for each move. Further, such moves of mobile bridge conveyors can cause down time that may significantly affect upstream operations or complicate scheduling associated with the stacking of material.
Conveyor systems used for stacking material may include a system configured for using radial stackers and grasshopper conveyors. The radial stacker in such systems is configured to work in a circular path and often has an extendable conveyor head to increase the time between stack moves. The system is set up at an initial location with the stacker at its initial position. Once the radial stacker completes its first rotation, the head of the stacker may be extended or retracted and the stacker could reverse its path to further stack material. This process may continue until the stacker has stacked a distance equal to the extension/retraction length of the extendable conveyor head. The stacker and single section bridge then may index forwards or backwards to a new location to stack additional material.
Movement to the new location often takes a significant amount of time. For instance, the stacker may need to be moved by a lifting device or by towing the stacker. In this type of system, the stacker tail end is often supported by the head end of a single section bridge conveyor. The single section bridge conveyor either pushes or pulls the stacker depending on whether the stacker is advance or retreat stacking. Grasshopper conveyors may be positioned adjacent to the single section bridge conveyor to transfer material to the single section bridge conveyor feeding the stacker. For advance stacking versions of this system, grasshopper conveyors may be added to the system. For retreat stacking versions of this system, grasshopper conveyors may be removed from such a system. Grasshopper conveyor systems are usually only used for retreat stacking.
As the single section bridge conveyor moves, it travels under the discharge of a unique grasshopper conveyor. Once the bridge conveyor has moved a distance equal to the length of a grasshopper conveyor, the grasshopper conveyor is removed or added for stacking material at another position. Movement of the single section bridge conveyor and stacker when adding or removing a grasshopper conveyor usually requires the system to be shut down. Additionally, movement of the grasshopper conveyors for adding or removing grasshopper conveyors typically requires the system to be shut down. Such shut downs require significant costs to be incurred.
Another example of a conveyor system that may be utilized to stack material includes use of a racetrack system often used for leach pad stacking. A racetrack system is often an on/off leach pad and is often used when there is limited space for a permanent leach pad or where leachate pumping costs are extremely high for a permanent pad. Racetrack systems are often rectangular in shape and there is usually one pad on each side of a conveyor corridor. A racetrack system typically uses a mobile stacking bridge conveyor for stacking material, a mobile receiving conveyor and a bucket wheel excavator for removing the leached material, and a central corridor with a feed overland conveyor and a reclaim overland conveyor. Typically, there is a generally semicircular area at each end of the pads in which a mobile bridge conveyor can rotate from one pad to another. Such systems provide little design flexibility, if any, for permitting stacking that may utilize irregular shaped space in storage areas.
A system for stacking or an apparatus configured for stacking material is needed that provides for the utilization of more space for stacking. Preferably, such a system is configured to permit a storage area to be in any dimension desirable for stacking of material, such as an irregular shaped stacking area that may include a number of hills or valleys.